1. Field of the Invention
This invention relates to electrical interconnections in integrated circuit structures, and in particular, to a process for forming interconnections between layers of electrically conductive material in integrated circuit structures.
2. Prior Art
Most integrated circuit manufacturing operations have relied upon aluminum or alloys of aluminum with copper or other materials for fabricating the interconnections between regions on the surface of an integrated circuit structure. The technology for fabricating such interconnections using aluminum is well known. Numerous techniques are also known for forming "vias" which are used to connect an underlying conductive layer to an overlying conductive layer otherwise separated by an intervening region of insulating material.
Unfortunately, aluminum interconnections in integrated circuit structures suffer from several disadvantages. Aluminum lines are prone to electromigration as the electric current flowing through the aluminum conductor progressively shifts aluminum atoms from one location to another, eventually causing failure of the connecting line. In addition, aluminum conductors, and many other metals or alloys, form oxides which make creating reliable ohmic connections to the conductor difficult. Further, because aluminum, and alloys of aluminum, melt at relatively low temperatures, subsequent processing of an integrated circuit structure after deposition of aluminum is necessarily limited. To overcome these and other disadvantages of aluminum interconnections, metal silicides are being increasingly studied as an alternative means of providing a high conductivity metallization system in integrated circuit structures. A recent publication indicative of this interest is "Refractory Silicides for Low Resistivity Gates and Interconnects" by S. P. Murarka, Technical Digest of the 1979 International Electron Devices Meeting, Washington, D.C., Dec. 3-5, 1979.